Field of the Invention
The present invention relates in general to machines for the preparation of beverages.
Background
More specifically the invention relates to a machine for the preparation of beverages of the type defined in the introductory part or preamble of the accompanying claim 1.
A machine of this type is described in the German patent application No. DE 102009045069 A1. In this machine according to the prior art a microphone sensor connected to a microcontroller is provided. The microcontroller is designed to detect, from an analysis of the signal of the microphone sensor, the first stroke of the pump (which is of the plunger type) following activation of the pump and to determine the duration during the time interval between activation and said first stroke. From this information the microcontroller deduces the flowrate of the flow generated by the pump and thus avoids the use, for this purpose, of a flowmeter, which is a relatively costly device.
These machines for the preparation of beverages, in particular hot beverages, for example coffee, with or without the use of capsules or pods containing prepackaged doses, are widespread both for use in a home environment and for use in a public place, for example in offices and the like.
In these machines, in order to prepare a beverage, a pump, for example of the vibration type, is activated, which inevitably generates an acoustic noise, the level of which may in some cases be somewhat bothersome.
In the machine according to DE 10 2009 045069 A1 the microphone sensor may also be used to detect the noise generated during operation of the pump and to drive the pump so as to reduce the bothersome noise generated.
The pumps used in such machines for the preparation of beverages are inevitably subject to dimensional tolerances and tolerances for the mechanical and/or electrical characteristics of their components. Owing to these tolerances of the components, as well as the assembly tolerances, the individual pumps of a same type produce in general, when excited by a current with predetermined characteristics, a noise with different characteristics and generate liquid flows with different flowrates.
This has the effect that machines which are nominally identical and equipped with pumps which are nominally identical may produce beverages with characteristics which are significantly different from each other.
An object of the present invention is to provide a machine for the preparation of beverages which is able to overcome said drawback of the machines according to the prior art.